Means for preventing sparking in direct-current machines.



I "A. FAHRMBACHER.

MEANS FOR PREVENTING SPARKI-NG IN DIRECT CURRENT MACHINES.

APPLICATION FILED OCT- 22. I9I 2.

Patented Feb.13,1917.

UNITED STATES PATENT OFFICE.

ALOIS FAI-IRMBACI-IER, OF GHARLOTTENBURG, GERMANY, ASSIGNOR TO SIEMENS- SCHUCKERT WERKE, G. M. B. H., OF BERLIN, GERMANY, A C )RPORATION OF GER- MANY.

MEANS FOR YREVENTING SPABKING IN DIRECT-CURRENT MACHINES.

Application filed October 22, 1912.

To, all whom it may concern:

Be it known that I, Annie FAHRMBACIIER, a citizen of the German Empire, and residing at Charlottenburg, near Berlin, Germany, have invented certain new and useful ing in direct-current machines of the type described in the application Serial No. 651,794, filed September 28, 1911. by. Ludwig Binder of Berlin, Germany, and a primary object is to obtain a commutating field which is as favorable as possible with a wide range of speed.

To this end, I provide the auxiliary machine with a second field winding which opposes the main field-winding thereof through which flows the main current or a part of the same.

The invention consists in the combination of parts described hereinafter and pointed out in the claims.

The invention is diagrammatically repre sented in the accompanying drawing, where- 1n Figure l is a diagram showing the variation of connnutating fields with the speed;

Fig. 2 shows one form of my invention in which the auxiliary machine has a self-exciting shunt winding which opposes the main fieldwinding thereof;

Fig. 3 shows another form, in which the auxiliary machine has a counter compounding winding;

Fig. 4 shows a modified form corresponding to that shown in Fig. 3, but in which the main field-winding of the auxiliary machine is connected in parallel. with the commutating winding of the main machine;

Fig. 5 shows another modification in which the main field-winding of the auxiliary machine is connected in shunt to the compensat-ion winding of the main machine;

Fig. 6 shows another modification in which the main field-winding of the auxiliary machine is connected in shunt across both the compensation winding and the com mutating winding of the main machine, and

Fig; 7 shows a simplified form of the inventioln.

In the abovsaiastiofi Serial Specification of Letters Patent.

Patented Feb. 13, 1917.

Serial No. 727,131.

No. 651,794 an arrangement for preventing sparking in direct-c1 rrent.1nacl1ines is described, in. which l3l1t commute-ting field is influenced by an auxiliary machine which runs synchronously with the main machine and works on a second coininutating winding connected opposit l y to the commutating winding proper; Consequently, when the speed increases the commutating field is weakened. A comma :ating field is obtained which corresponds "airly exactly to the curve I in Fig. 1 w iich indicates the dependence of the comnuitating field F on the number of revolution; N when the strength of current remains co JSiJflIlt.

Now it has been for nd by tests that such a commutating field indicated by the curve I does not result in H e most favorable commutating conditions. On the contrary, a. commutating field cu] ve as indicated by the curve II inFig. 1 would correspond to the most favorable commutation. This curve II at first runs approximately coincident with curye I; at high speeds, however, it runs approximately parallel with the axis of the abicissae.

Now in order to obtain as favorable a commutating field cufive as possible, I provide the auxiliary machine with a second field-winding which cpposes the main field winding through which the main current or a part of the same p2 sses.

Such an arrangement is shown for example in Fig. 2. The ma in machine is here designated a, while it der otes the auxiliary machine; f is the main fieldwinding ofthe main machine and e the main field-winding of the auxiliary macl". ine. In this arrangement the auxiliary ma chine is provided with a self-exciting shunt winding 'n which acts Consequently, in this arrangerepresented by curve II in Fig. 1 is obtained. T he action of the. shunt winding corresponds to the difference d of the curves I and II which is onl 7 small at low speeds, while it is greater at l igh speeds.

A similar eflect is obtained by the arrangement represented in Fig. 3,- in which the auxiliary machine h is provided with .a

counter compound winding /t' which likewise opposes the main fiehl-winding e. Accord ing to the invention it is thus immaterial whether the second winding n or is of the auxiliary dynamo be fed in series or in shunt by the armature h. It is essential, however, that the second field-winding n or Z: shall oppose the main field-Winding 6. Moreover, the main field-winding 6 may be fed in series by the main current, as is represented in Figs. 2 and 3.

On the otherhand, as shown by way of example in Fig. 4, which otherwise corre sponds with the arrangement shown in Fig. 3, the field winding ema v be connected in parallel with the commuL-mug winding 10 of the main machine, or, as in Fig. 5, be con tween the armature current and the auxiliary machine current. \Vhen the speed increases the electromotive force of the auxiliary machine increases, the current in the circuit h, w, 1' is increased and the current in the conunutating winding decreases correspondingly. Too great increase of current can be prevented by means of a resistance 1" connected in the auxiliary machine circuit, this resistance being variable if desired.

In the present application I have directwl the claims to the general arrangement wherein the counter-action exerted upon the commutating winding is obtained by changing the voltage of -the auxiliary dynamo in the manner specified, while in a divi' cation filed Jan. 21, 1915, Serial No. 3527, I have confined my claims to the specific arrangement of an additional winding 2 which is supplied by the auxiliary dynamo for counteracting the commutating winding.

commutating winding )YhlCh 15 now traversed by the difference begeared to said main sional appli-- I claim 1. In a direct current dynamo electric.

machine of the character described, the combination of a main dynamo having a commutating winding; an auxiliary dynamo whose potential varies proportionately to the speed of the main dynamo for counteracting said cominutating winding at, increasing speed of said main dynamo; and voltage varying means for more slowly increasing the voltage of said auxiliary dynamo at relatively high speed and more ra idly in creasing the sameat relatively alow speed,

both as a predetermined function of the winding on said auxiliary dynamo connected to oppose the action of said main fieldwinding.

3. In a direct current dynamo electric machine of the character described, the combination of a main dynamo haying acom mutating Winding; an auxiliary dynamo dynamo; a niain fieldwlnding on said auxiliary dynamo which is connected to be energized in dependence on the curreli t generated by the armature of said main dy'namo; a self-exciting winding on said auxiliary dynamo'which is connected to oppose the action of themain field-wind- .ing thereof; and connections between said auxiliary and said, main dynamo for opposing the action of said commutating winding at increasing speed of said main and auxiliary dynamo.

In testimony whereof,

two witnesses. e ZAL'OIS FAI-IRMBAGIIER. Witnesses: a I WOLDEMAR I'IAUPT,

HENRY HAsrnn.

I have'signedinyname to this specification in the presence of 

